"There is nothing to worry us in terms of Swedish and Finnish membership of NATO," Putin told journalists in Asghabat. "We don't have problems with Sweden and Finland like we do with Ukraine... They can join whatever they want."
Nonetheless, Putin stressed that Moscow would respond in the event of military buildup in the region.
"They must clearly understand that previously there were no threats to them — but if troops are stationed there and infrastructure established, we will have to respond accordingly and make the same threats to the territory from where threats to us are coming," he added.
Putin went on to say that there will be "some tension" between the two countries and Moscow.
Russia's president accused NATO of seeking to assert its "supremacy" and "imperial ambitions," as well as using the Ukrainian people as a "means" for the alliance to "defend its own interests." He also said that the West was trying to turn Ukraine into an "anti-Russia."
Sweden and Finland to join NATO
At a summit on Wednesday, NATO invited Sweden and Finland to join the alliance, initiating the membership process for the two Nordic countries. Both Helsinki and Stockholm had previously maintained military non-alignment.
The expansion of the alliance will extend its land border with Russia by more than 1,300 kilometers (808 miles) of the Finnish-Russian border.
Finnish Foreign Minister Pekka Haavisto told DW that Finland wants this border to remain a peaceful border.
"We have normal border cooperation with Russia. We have people coming and going. We are issuing visas in our embassy in Moscow and our consulate in St Petersburg, and of course we would like to have that relation with Russia as normal as it can be in these conditions," Haavisto said.
He also said that Finland was avoiding all the provocations against Russia in these circumstances, but taking care of its own defense and security, citing its purchase of 64 US-made F-35 combat aircraft as one example.